PDFtk is a simple "tool kit" for doing everyday things with PDF documents. It comes in three flavors: PDFtk Free, PDFtk Pro, and a command-line tool PDFtk Server.
 PDFtk Free
PDFtk Free is a friendly graphical tool for quickly merging and splitting PDF documents and pages. It is free to use for as long as you like. It is available for Windows machines.
 PDFtk Pro
Use PDFtk Pro to quickly split, merge, rotate, watermark, stamp and secure PDF pages and documents. PDFtk Pro is a graphical application that makes working with PDFs as easy as possible. PDFtx Pro costs $3.99 It is available for Windows machines.
PDFtk Pro can add secure protection using the standard AES128 user_pw feature
 PDFtk Server
For Power Users PDFtk Pro and PDFtx Free comes with their command-line tool, PDFtk Server. So you get both the GUI and the command-line interface to PDFtk!
PDFtk Server is their original command-line tool. It is commonly used for server-side processing of PDFs. It is also used by many PC software publishers to give their products the ability to manipulate PDFs.
PDFtk Server can:
- Merge PDF Documents or Collate PDF Page Scans
- Split PDF Pages into a New Document
- Rotate PDF Documents or Pages
- Decrypt Input as Necessary (Password Required)
- Encrypt Output as Desired
- Fill PDF Forms with X/FDF Data and/or Flatten Forms
- Generate FDF Data Stencils from PDF Forms
- Apply a Background Watermark or a Foreground Stamp
- Report PDF Metrics, Bookmarks and Metadata
- Add/Update PDF Bookmarks or Metadata
- Attach Files to PDF Pages or the PDF Document
- Unpack PDF Attachments
- Burst a PDF Document into Single Pages
- Uncompress and Re-Compress Page Streams
- Repair Corrupted PDF (Where Possible)